diff --git a/scrapy/extensions/httpcache.py b/scrapy/extensions/httpcache.py
index 3f4af42b7..b7219bf07 100644
--- a/scrapy/extensions/httpcache.py
+++ b/scrapy/extensions/httpcache.py
@@ -370,12 +370,11 @@ class FilesystemCacheStorage:
         with self._open(rpath / "pickled_meta", "wb") as f:
             pickle.dump(metadata, f, protocol=4)
         with self._open(rpath / "response_headers", "wb") as f:
-            # headers_dict_to_raw() needs a better type hint
-            f.write(cast(bytes, headers_dict_to_raw(response.headers)))
+            f.write(headers_dict_to_raw(response.headers))
         with self._open(rpath / "response_body", "wb") as f:
             f.write(response.body)
         with self._open(rpath / "request_headers", "wb") as f:
-            f.write(cast(bytes, headers_dict_to_raw(request.headers)))
+            f.write(headers_dict_to_raw(request.headers))
         with self._open(rpath / "request_body", "wb") as f:
             f.write(request.body)
 
diff --git a/scrapy/http/headers.py b/scrapy/http/headers.py
index 73aee7178..85b9229d3 100644
--- a/scrapy/http/headers.py
+++ b/scrapy/http/headers.py
@@ -118,8 +118,7 @@ class Headers(CaselessDict):
         ]
 
     def to_string(self) -> bytes:
-        # cast() can be removed if the headers_dict_to_raw() hint is improved
-        return cast(bytes, headers_dict_to_raw(self))
+        return headers_dict_to_raw(self)
 
     def to_unicode_dict(self) -> CaseInsensitiveDict:
         """Return headers as a CaseInsensitiveDict with str keys
diff --git a/tox.ini b/tox.ini
index 5a5e80496..023a86c5a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -47,18 +47,17 @@ install_command =
 basepython = python3
 deps =
     mypy==1.10.0
-    typing-extensions==4.11.0
+    typing-extensions==4.12.1
     types-lxml==2024.4.14
     types-Pygments==2.18.0.20240506
     types-pyOpenSSL==24.1.0.20240425
-    types-setuptools==69.5.0.20240518
+    types-setuptools==70.0.0.20240524
     botocore-stubs==1.34.94
-    boto3-stubs[s3]==1.34.108
+    boto3-stubs[s3]==1.34.119
     attrs >= 18.2.0
     Pillow >= 10.3.0
     pytest >= 8.2.0
-    # 2.1.2 fixes a typing bug: https://github.com/scrapy/w3lib/pull/211
-    w3lib >= 2.1.2
+    w3lib >= 2.2.0
 commands =
     mypy {posargs: scrapy tests}